Orthodontic bracket for use on deciduous teeth

ABSTRACT

The present invention relates to orthodontic brackets designed for use with the deciduous teeth and method for its use. The brackets provide one or more debonding tabs which reduces the potential for damage to the deciduous tooth due to the application of excessive force during the debonding process. The small size of the brackets allow the brackets to fit available crown space on the deciduous teeth. Further the brackets are shaped to minimize mechanical forces applied to the deciduous teeth when engaged with an archwire. The bracket bases are shaped to conform to the morphology of the deciduous tooth crown surface thereby providing an optimal adhesive interface with the deciduous tooth. The deciduous brackets provide proper adhesion to avoid unwanted detachment of the brackets which often occurs when the use of permanent brackets is attempted on the deciduous teeth.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation U.S. application Ser. No. 13/050,385filed on Mar. 17, 2011, which is incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to the use of orthodontic brackets on deciduousteeth to correct tooth alignment.

BACKGROUND OF THE INVENTION

One type of common orthodontic treatment involves the use of a set oftiny appliances commonly known as brackets and buccal tubes. Buccaltubes are normally mounted on the molars and brackets are attached toall other teeth. Each bracket is secured to a corresponding tooththrough a bonding adhesive which is sandwiched between the pad ofbracket on one side and enamel surface of the tooth on the other side.Each bracket has a slot to receive a resilient archwire. The slot formsa track to guide movement of the teeth to desired positions. Ends ofarchwire are commonly placed in slots or channels of buccal tubeappliances that are attached to the molar teeth either through bondingwith adhesive or first welded on a band and then cemented on the tooth.

Use of Brackets on Deciduous Teeth

Up to the present time, the orthodontic brackets and tubes (braces)which are available in the market have been designed for permanentteeth. Several forms of bite problems (malocclusion) develop duringchildhood in the deciduous (primary) dentition. Most common amongst themare cross bites of the anterior or posterior teeth. The advances in ourunderstanding of children growth and development and in interceptiveorthodontics have made the treatment of younger children more desirable.

Such treatment is done during the deciduous (primary) dentition orduring mixed-dentition period when the deciduous teeth are stillpresent. There are circumstances that early correction of a malocclusionduring deciduous or mixed-dentition periods would either prevent orreduce the extent of treatment at a later date.

Deciduous teeth can be moved to allow better jaw relationship, to makeroom for the permanent teeth or used as anchors for more efficientmovement of the permanent teeth. Malocclusions that involve deciduousteeth are simpler and easier to correct that malocclusion of permanentteeth. This is due to the younger age of the patients for whom thetissues surrounding deciduous teeth are more adaptive and allow fastermovement of the deciduous teeth with smaller increments of force.

Due to a lack of availability of brackets and tubes for the deciduousteeth, the orthodontists are forced to either defer the treatment toallow the development of permanent dentition or use the appliances thatare designed for permanent teeth and place them on the deciduous teeth.Due to different size and shape of these teeth the permanent teethbracket bases do not adapt well to the deciduous teeth surfaces.Further, studies performed in Japan (American Journal of Orthodonticsand Dentofacial Orthopedics Vol. 134/2008 pp. 198-208article—“Comparison of shear bond strengths of orthodontic bracketsbonded to deciduous and permanent teeth” by Endo, T. et. al.) have shownthat permanent brackets bond more weakly to deciduous as opposed topermanent teeth. The researchers attributed the weak bonding to adifference in the chemical structure of the enamel found on deciduousteeth as compared to permanent teeth. As a result of these and otherfactors, brackets bonded to deciduous teeth frequently come loose duringthe course of treatment creating inconvenience and frustration for boththe patient and the dentist.

Additionally, the mode and rate of movement of deciduous teeth isdifferent from permanent teeth. The brackets that are designed forpermanent teeth are too large for the deciduous teeth thereforeinterfere with proper brushing, cause impingement of the gum tissues andapply several unnecessary force vectors on the deciduous teeth.

Debonding

Debonding brackets from deciduous teeth may also be a problem. Deciduousteeth become progressively looser prior to falling out due to theresorption of their roots. Therefore they may not have the structuralintegrity to easily sustain the pressure required for removal of abracket as would a permanent tooth.

Metal brackets are commonly debonded using a plier-type hand instrument.Force is typically applied in the mesial-distal or diagonal directioncausing deformation in the ductile bracket body. This deformationeffects a separation or fracture at the interface between the bondingadhesive and the bracket base allowing the bracket to be peeled or priedaway from the tooth surface.

DESCRIPTION OF RELATED ART

Brackets made of materials more brittle than metal, such as ceramic, arenot easily peeled or pried away from the tooth surface and tend tofracture under an applied force. An attempt to apply mesial-distal forceas described with metal brackets generally results in the fracture ofthe tie wings or other portions of the bracket. Various tools have beenput forward to remedy this problem (e.g. U.S. Pat. No. 4,950,157 toCleary, U.S. Pat. No. 4,904,183 to Hannan and U.S. Pat. No. 6,382,965 toRuiz-Vela), but none has provided a complete solution.

U.S. Pat. No. 5,439,379 to Hansen discloses an orthodontic bracketdesign, the purpose of which is to facilitate the debonding of ceramicorthodontic brackets. The disclosed design provides for a bracket withmesial and distal sections separated by an elongated channel extendinggenerally in the occlusal-gingival direction. During debonding thepressure applied with a tool such as pliers causes the mesial and distalsections to pivot towards each other, thereby applying pressure to thebonding surfaces. In theory this design puts significantly less stresson the bracket in order to effectuate debonding than would be the casewith a conventional ceramic orthodontic bracket.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to an orthodontic bracket specificallydesigned for use with the deciduous teeth and method for its use. Thedeciduous teeth have been shown by various practitioners to beparticularly useful anchors for the alignment of permanent teeth whenintegrated into a dental appliance. The bracket is unique in providing adebonding tab which reduces the potential for damage to the tooth due tothe application of excessive force during the debonding process. Thesmall size of the bracket allows it to fit available crown space on thedeciduous teeth. Further the bracket is modified in shape to minimizemechanical forces applied to the deciduous teeth when engaged with anarchwire. The bracket base is shaped to conform to the morphology of thedeciduous crown surface thereby providing an optimal adhesive interfacewith the deciduous tooth. The deciduous bracket provides adequateadhesion to avoid unwanted detachment of the bracket which often occurswhen the use of permanent brackets is attempted on the deciduous teeth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a deciduous bracket.

FIG. 2 is a buccal view of a deciduous bracket.

FIG. 3 is a second perspective view of a deciduous brackets showing baseindentations.

FIG. 4 is an occlusal view of a deciduous bracket designed for use on adeciduous lower second molar.

FIG. 5 is an occlusal view of a deciduous bracket designed for use on adeciduous lower first molar or upper deciduous first molar or upperdeciduous second molar.

FIG. 6 is an occlusal view of a deciduous bracket designed for use on adeciduous canine tooth.

FIG. 7 depicts the process of debonding a deciduous bracket from adeciduous tooth prior to introduction of the debonding tool.

FIG. 8 depicts the process of debonding a deciduous bracket from adeciduous tooth with the debonding tool in an intermediate position.

FIG. 9 depicts the process of debonding a deciduous bracket from adeciduous tooth where debonding has been completed.

FIG. 10 is a side view of a dental appliance on mixed dentition andhaving both deciduous brackets and permanent orthodontic brackets.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable any person skilled inthe art to make and use the disclosed embodiments, and is provided inthe context of a particular application and its requirements. Variousmodifications to the disclosed embodiments will be readily apparent tothose skilled in the art, and the general principles defined herein maybe applied to other embodiments and applications without departing fromthe spirit and scope of the present description. Thus, the presentdescription is not intended to be limited to the embodiments shown, butis to be accorded the widest scope consistent with the principles andfeatures disclosed herein.

For the purposes of this disclosure the term “deciduous bracket” refersto an orthodontic bracket particularly designed for use on a deciduoushuman tooth.

Orthodontic treatment is defined as correction of misaligned teeth andimproper bite. Alignment of crooked teeth and correction of biteproblems are accomplished by devices that are referred to as orthodonticappliances. The most common type of orthodontic appliances are calledfixed appliances or braces. Fixed appliances include tiny pieces calledbrackets which are secured to the teeth and serve as handles to move theteeth. Brackets have a slot to receive an arch wire. Bracket slots forma track to guide movement of the teeth to desired positions. Ends of thearchwire are commonly placed in channels called buccal tubes which aremounted on the patient's molar teeth. Brackets and buccal tubes arecollectively called attachments.

A large proportion of orthodontic treatment is done around adolescencewhich corresponds with completion of the so called permanent dentition.For this reason, the orthodontic attachments are designed to optimallyfit the permanent teeth. However, misalignment of teeth and improperbite (malocclusion) usually become noticeable in early mixed-dentitionat the age of about seven. In this stage of a child's development, thepermanent first molars erupt in the posterior region of the mouth andthe permanent incisors erupt in the anterior region. Deciduous canines,first and second molars which are interposed between the permanent firstmolars and incisors continue their presence and function for at leastfour more years in the buccal segments, hence the term mixed dentition.

For many forms of malocclusion the mixed-dentition period provides anoptimal treatment time. The treatment that commences duringmixed-dentition is called interceptive orthodontic treatment. There arerare circumstances that treatment is indicated prior to mixed dentitionperiod, in children younger than seven years of age, during the socalled deciduous dentition. Treatment that is initiated inmixed-dentition has to consider the presence of the deciduous teethwhich occupy a significant portion of the dental arches. At the presenttime a practitioner who engages in interceptive orthodontic treatment,has two choices:

1. Placement of the attachments on the permanent teeth and bypassing thedeciduous teeth in the dental arch. The appliance design used in thistechnique is commonly called the 2 by 4 appliance. Generally speaking,the 2 by 4 approach is inefficient due to the long, unsupported spans ofarch wires that connect the permanent molars to permanent incisors.

2. Inclusion of the deciduous teeth in the appliances by using thebrackets of permanent teeth and placing them on the deciduous teeth aswell as the permanent teeth. In this approach the brackets do not adaptwell to the deciduous teeth and detach frequently causing delays anddiscomfort for the practitioner and patient.

The present invention involves a new design brackets specifically forattachment to the deciduous teeth. A major feature of the deciduousbrackets is the bracket base which is adapted to the surface morphologyof the deciduous molars and canines.

Advantages of Using Deciduous Teeth in Interceptive Treatment

Deciduous teeth can be used as anchors to move the permanent teeth moreefficiently. They can also be moved to allow more space for thepermanent teeth. Using brackets on the deciduous teeth and theirinclusion in the mechanics of tooth movement increases the efficiency ofthe appliances in the following circumstances:

1. Correction of crowding: Development of additional space and thesupportive structures for permanent teeth is accomplished throughexpansion of the posterior segments. In the maxillary arch a rapidpalatal expansion appliance is used to expand the maxilla using thepermanent and deciduous teeth in the posterior segments as anchors. Oncethere is adequate space, the deciduous teeth and permanent incisors arebracketed. A series of arch wires are used for leveling and alignment ofthe incisors using deciduous canines as anchors for alignment of theincisors. Due to proximity of the deciduous canines to the permanentincisors, they serve as ideal anchor teeth for efficient alignment ofthe incisors. In the mandibular arch a removable lingual arch isemployed initially to expand the permanent first molars. The deciduouscanines and molars are bonded along with the permanent incisors onceadequate expansion of the permanent molars is achieved. The deciduousmolars and canines are expanded and incisors are leveled and alignedwith a series of arch wires using permanent molars as anchors.

2. Correction of deep bite and open bite cases: Intrusion and extrusionof the permanent incisors are facilitated by using the deciduous teethas anchors. In the maxillary arch the deciduous canine brackets areangled either upward or downward to apply the corresponding bite openingor closing forces to the maxillary incisors. In the mandibular archopening of bite is facilitated by progressively positioning thedeciduous brackets more gingival and by tilting them so that theirmesial aspects point downward from the second deciduous molar todeciduous canine.

3. Correction of cross bites: There are many different types of crossbite which require different approaches to their treatment plan.Deciduous brackets can offer more efficient means of correcting varioustypes of cross bites. For correction of a complex cross bite involvingboth upper and lower dental arches, expansion of maxilla and mandibulararch are accomplished with a maxillary expansion appliance (MEA) and alower lingual arch (LLA) respectively. Maxillary incisors are advancedusing stops in the arch wires. Mandibular incisors are retracted usingthe additional space provided by expansion of the permanent anddeciduous molars and canines. In the correction of skeletal cross bitesdue to a maxillary under development, a face mask or reverse pull headgear can be employed. Intermaxillary elastics can also be also be usedfor additional effects. In the cases of simpler forms of cross bitessuch as those involving one arch or only a portion of the dental arch,the mechanics should be simplified to reflect the less complex nature ofthese cases.

4. Correction of impacted permanent first molars: Occasionally, thepermanent first molars develop ectopically under the distal bulge of thedeciduous second molars. The affected permanent molar can be correctedthrough sectional mechanics with bonded brackets on the adjacentdeciduous molars and the impacted first molar. The present inventionprovides the practitioners with simple and inexpensive attachments forthe deciduous teeth. The anatomically designed bases of theseattachments allow adequate adaptation to the surface of the deciduousteeth and therefore bond reliably to the enamel of the deciduous teeth.Inclusion of the deciduous teeth in the mechanics of tooth movementincreases the efficiency of the appliances and provides new andinnovative approaches for the treatment of children duringmixed-dentition

FIG. 1 shows a perspective view of an embodiment of a deciduous bracket10. In this embodiment bracket base 30 conforms to a deciduous toothcrown surface by means of two base indentations 32. This arrangement ofindentations is particularly well adapted for use on a deciduous firstmolar. Debonding tab 40 is a horizontal extension of the buccal bodysurface 20 situated in this embodiment on the mesial side of deciduousbracket 10. Tie wings 22 allow for the engagement of an archwire.

FIG. 2 is a buccal view of deciduous bracket 10. The occlusal-gingivaldimension 22 and mesio-distal 23 dimension of deciduous bracket 10 areboth uniquely sized to provide maximum surface area contact betweendeciduous bracket 10 and a deciduous tooth. Maximizing the bracketsurface area in contact with the deciduous tooth crown surface is animportant factor in maintaining a solid bond between a deciduous bracketand the crown surface of a deciduous tooth. The debonding tab width 41of debonding tab 40 determines the size of the access area available forinteraction with a debonding tool, as further explained below.

FIG. 3 is a second perspective view of an embodiment of deciduousbracket 10. Two indentations 32 of bracket base 30 are shown.Directional arrow 37 describes the mesio-distal radius of a baseindentation 32. The mesio-distal radius of a base indentation 32 canrange from about 3 to about 4.5 mm. The radius in the occlusal-gingivalplane is represented by directional arrow 35 and can range from about4.5 to about 6.5 mm. Curvature of the bracket base indentationscorresponding to these radii provide for optimal bonding between abracket surface and the corresponding deciduous tooth crown surface.Also shown in FIG. 3 is debonding tab 40 and the debonding tab lingualsurface 42. It can be seen here that debonding tab lingual surface 42 isrecessed buccally as compared to the bracket base 30, thereby formingdebonding access area 80 (FIG. 8) beneath the debonding tab.

FIG. 4 shows an occlusal view of an embodiment of deciduous bracket 10designed specifically for use on a lower deciduous second molar 81. Itcan be seen that the base indentations 32 correspond to cusps 84 of thedeciduous lower second molar 81 to facilitate tight bonding using aminimal amount of adhesive. Directional arrow 25 describes the overallradius of bracket base 30. The radius for this embodiment can range fromabout 8 to 11 mm. and corresponds to the overall curvature of the buccalcrown surface 83 of deciduous second molar 81. In this embodimentdebonding tab 40 extends mesially from the buccal body surface 20 ofdeciduous bracket 10.

FIG. 5 shows an occlusal view of an embodiment of deciduous bracket 10designed for use on a lower deciduous first molar 91. This particularembodiment can also be used on an upper deciduous first molar (notshown) or upper deciduous second molar (not shown). Again it can be seenthat the base indentations 32 correspond to cusps 94 of the deciduouslower first molar 91 to facilitate tight bonding. Directional arrow 25describes the overall radius of bracket base 30. This radius for thisembodiment can range from about 3 to about 11 mm. and corresponds to theoverall curvature of the buccal crown surface 93 of deciduous firstmolar 91.

FIG. 6 is an occlusal view of an embodiment of deciduous bracket 10 foruse a deciduous canine tooth 101. In this embodiment the base surface 39is smoothly curved to conform to occlusal surface 103 of deciduouscanine tooth 101. Radius arrow 25 describes the overall radius ofbracket base 30. The radius for this embodiment can range from about 2to 4.5 mm. Debonding tab 40 extends occlusally from buccal body surface20 of deciduous bracket 10.

FIG. 7-FIG. 9 depicts the debonding process as it would occur on anydeciduous tooth. The lingual surface of the debonding tab provides aconvenient access area for a debonding tool allowing removal of thebracket from a tooth while exerting minimal pressure on the tooth. Thisis important since deciduous teeth become progressively looser as achild ages and the pressure required for bracket removal can be quiteuncomfortable for the child. FIG. 7 is a perspective view of deciduousbracket 10 attached to the buccal crown surface 92 of a deciduous firstmolar 91. The tips 72 (shown in FIG. 8) of debonding tool 70 areinserted beneath debonding tab 40 as an initial step in the debondingprocess. FIG. 8 is a cross sectional view of deciduous bracket 10 asseen along reference line 8,9 of FIG. 7 Again we see deciduous bracket10 attached to the buccal crown surface 92 of deciduous first molar 91during the initiation of the debonding process. Tips 72 of debondingtool 70 have been introduced into debonding access area 80 but are notyet in contact with lingual surface 42 of debonding tab 40. FIG. 9 showsthe same cross sectional view and features as FIG. 8, as seen alongreference line 8,9 of FIG. 7. Here, the tips 72 of debonding tool 70have been further inserted into debonding access area 80 and are incontact with both the lingual surface 42 of debonding tab 40 and thebuccal crown surface 92 of deciduous first molar 91. The simultaneousforces applied by the debonding tool against crown surface 92 anddebonding tab 40 effectuate debonding of deciduous bracket 10 fromdeciduous first molar 91.

FIG. 10 depicts one possible method of using deciduous brackets for thecorrection of misaligned teeth and bite problems on upper and lowermixed dentition dental arches. Dental appliance 124 is shown on upperand lower dental arches, 111 and 112 respectively. Dental appliance 124is comprised of deciduous brackets 10 on second deciduous molars 81,first deciduous molars 91 and deciduous canines 101. Dental appliance124 is further comprised of permanent brackets 120 attached to permanentteeth 126, and archwires 122.

The foregoing descriptions of embodiments have been presented forpurposes of illustration and description only. They are not intended tobe exhaustive or to limit the present invention to the forms disclosed.

Accordingly, many modifications and variations will be apparent topractitioners skilled in the art. Additionally, the above disclosure isnot intended to limit the present invention. The scope of the presentinvention is defined by the appended claims.

What is claimed is:
 1. A method of correcting tooth misalignment inmixed dentition, the method comprising: attaching a deciduous bracket toa buccal crown surface of a deciduous tooth as a component of a dentalappliance, wherein the dental appliance is further comprised oforthodontic brackets attached to one or more permanent teeth, andwherein the attached deciduous bracket comprises: a base attached to thebuccal crown surface of the deciduous tooth; a body comprising a firstbuccal surface facing away from the buccal crown surface of thedeciduous tooth and one or more tie wings for the attachment of anarchwire; and a debonding tab extending vertically away from the firstbuccal surface of the body with the base attached to the buccal crownsurface of the deciduous tooth and extending in a mesiodistal directionalong an occlusal side of the body, wherein the debonding tab comprisesa lingual surface facing and spaced in a buccolingual direction from thebuccal crown surface of the deciduous tooth with the base attached tothe buccal crown surface of the deciduous tooth, and wherein thedebonding tab defines a recess between the buccal crown surface of thedeciduous tooth and the lingual surface accessible by a debonding tool;employing a series of arch wires used for leveling and alignment of thepermanent teeth while using the deciduous tooth as an anchor; andremoving the deciduous bracket from the deciduous tooth using thedebonding tool by inserting the debonding tool between the lingualsurface of the debonding tab and the buccal crown surface of thedeciduous tooth and applying simultaneous force against the lingualsurface of the debonding tab and the buccal crown surface of thedeciduous tooth with the debonding tool from only the occlusal side ofthe body in order to remove the deciduous bracket from the deciduoustooth.